Paavo PylkkänenDept. of Cognitive Neuroscience and Philosophy, Univ. of Skövde, SwedenDept. of Philosophy etc., University of Helsinki, FinlandE-mail: email@example.com
Part 1: a brief overview of the philosophical problems of relating mind and matter Part 2: a brief presentation of quantum theory, leading to Bohm’s interpretation Part 3: the relevance of Bohm’s interpretation to the mind-body problem
Much of contemporary philosophy is committed to physicalism: everything is physical, or everything is in an appropriate way dependent upon the physical (“supervenience”)
Many philosophers find it difficult to simply reduce the mental to the physical, and they thus defend non-reductive physicalism: mental properties are non-physical properties which, however, depend or “supervene” upon the physical.
The trouble with non-reductive physicalism: it seems to leave the mental causally inefficacious or epiphenomenal. if the mental is non-physical, it seems impossible to understand how the mental could be the cause of physical effects dependence/supervenience doesn’t help
Philosophers (e.g. Yablo, Lewis, Kim) have developed some ingenious ways to make the idea of genuine mental causation plausible. however: it seems that even these fail to tell us how mental properties (conceived as non- physical) could possibly influence the physical course of events
There thus seems to be no genuine role for mental properties in contemporary physicalism. this is a very unsatisfactory situation. however, to go back to, say, interactive substance dualism seems equally unsatisfactory. Thomas Nagel has summarized the situation: “Neither dualism nor materialism seems likely to be true, but it is not clear what the alternatives are.”
The alternative explored here: let us look at science in more detail. It has been known for a long time that the main theories of modern physics, quantum theory and relativity require radical changes in our view of matter.
A true “physicalist” needs to consider the mind-body problem in relation to our best scientific view(s) about the body It could be the case that quantum theory and relativity say nothing that is relevant to the mind- body problem However, this issue cannot be settled without careful examination!
What happens if you pass e.g. electrons through the 2-slits? The electron was initially assumed to be a particle (it has mass and charge) So we expect that it should behave like a little bullet
Notice that we get an interference pattern even if the electrons enter the slit system one by one
An individual system exhibits both particle properties ▪ it arrives at the detector at a single spot and wave properties ▪ the place where the spot appears is constrained by the mathematics of wave behaviour ▪ how else would such individual particles build up a wave interference pattern?
Natural to ask: how does the electron move through the slit system? How could a particle obey the mathematics of waves? The easiest way to answer these questions would be to make further experiments “Let’s look what happens”
Unfortunately we cannot observe the motion of an individual electron in detail! This relates to the Heisenberg indeterminacy principle “If we observe precisely where it is, we have no idea of where it is going” (and vice versa)
Note especially: to predict the movement of an electron we should measure both position x (“where it is”) and momentum p (“where it is going”) at a single moment. we cannot do this as long as we stay within current quantum theory! without the initial conditions we cannot predict what the individual system does! ▪ -> indeterminism, probability…
The mystery is this: the electrons leave as particles, and they arrive as particles, one by one, to the screen. as a large number of them passes through the system, a pattern builds up. what is this pattern? it is an interference pattern! interference is a signature of a wave.
But how can the particles, sent into the system one by one, collectively build up an interference pattern? Surely each individual “particle” must also have some wave property how otherwise could such a “particle” obey the interference pattern (avoid certain areas)?
Bohm’s interpretation postulates that the electron is a particle and a field
It is a common strategy in science to postulate a theory or hypothesis to explain some phenomena that we are interested in “Theorists postulate unobservable entities, and specific laws governing them, because occasionally this produces a theory that allows us to construct predictions and explanations of observable phenomena hitherto unexplained.” Churchland 1988: 71
So: Bohm’s interpretation resolves wave- particle duality by postulating that an electron is a particle always accompanied and guided by a new type of field.
In the two-slit experiment the particle goes through one of the slits, and then appears at a point in a photographic place this explains why we see the appearance of a spot note especially that there is no need to assume a collapse of the wave function The accompanying field goes through both slits, interferes afterwards, and guides the movement of the particle so that the particles collectively, spot by spot, build up an interference pattern.
The field gives rise to a new type of potential energy which Bohm called the “quantum potential”
Note: R appears both in denominator and numerator so that it can be multiplied by an arbitrary constant without changing Q. size doesn’t matter here, as a small wave can have exactly the same effect as a large one! this means that Q (and thus the effect on the particle) can be strong even if the amplitude of the quantum field is very weak.
What matters then? Note that Q depends on the second spatial derivative of R This reflects the way in which R changes, or the form of the wave. Thus, Q depends only upon the form of the quantum wave!
Bohm & Hiley: the quantum field is not pushing and pulling the particle mechanically Rather, it is putting form into the activity of the particle, literally IN-FORMING the energy of the particle-> A new notion of active information!
The basic idea of active information is that a form having very little energy enters into a directs a much greater energy. The activity of the greater energy is given a form similar to that of the smaller energy
Ship on autopilot, guided by a radar wave DNA molecule guiding biological processes reading a map
SHANNON INFORMATION ACTIVE INFORMATION A quantitative measure of Not essentially related to information that our knowledge or lack of it represents the way in e.g. information that is which the state of a system relevant to determining the is uncertain to us movement of the electron itself e.g. we can only specify information for the electron probabilities of various states information as an “objective commodity”
As we come to the psychological domain, it seems obvious that information is a key factor of mental phenomena. this has, of course, been recognized in cognitive science, with its assumption that the human brain/mind can be seen as a system that receives and stores information, and uses such information in the intelligent control of behaviour.
Bohm’s radical suggestion is that there is at least a strong analogy between the operation of information at the quantum level, and the operation of information at the various levels of mind.
We saw above that the suggestion is that at the quantum level information acts – it actively guides the movement of particles. Similarly, in human subjective experience, information content acts.
When I see something that in a given context means “danger” (e.g. a snake), this information content acts within the brain via electric action potentials also via various neurochemical processes to prepare the body for appropriate response (cf. Thagard (2002))
Bohm emphasizes that “…this is not merely a mental process, but includes an involuntary and essentially unconscious process of hormones, heart-beat, and neurochemicals of various kinds, as well as physical tensions and movements” (1990).
But how does information content act upon matter? how does such an abstract quality as the experienced meaning of information (e.g. “danger”) result in a wide range of electrical and chemical processes in the brain?
This question is very difficult to answer in contemporary philosophy of mind, which is still based upon a very strict division between the categories “physical” and “mental” (see Kim 2006).
Meaning is typically considered to be located at the “mental” side of the division, and there is currently no coherent theory that explains how meaning qua meaning can influence physical processes.
It is assumed that meanings are typically carried by some physical “vehicles” any causal influences associated with meaning are assumed to be the result of the operation of the physical vehicle that carries the content or meaning. The meaning itself is assumed to be causally inefficacious.
Notice that in Bohm’s model of the electron, the information is carried by the quantum field that is a qualitatively new type of field in physics that has some very exotic properties influences the movement of particles via its form lives in a multidimensional configuration space is able to mediate EPR-type non-local influences between particles
Thus we have a more subtle aspect (information in the quantum field) guiding the behaviour of a more manifest aspect (the particle)
We could generalize this to a principle that applies whenever meaning influences matter in other contexts. Bohm proposed such a principle and called it “soma-significance”. In this terminology a process in which meaning organizes the more manifest levels of matter is called a “signa-somatic” process.
Thus, in the context of the human mind we could speculate that information contained in mental processes and conscious experience is carried by some fairly subtle medium.
Of course, it seems likely that a great deal of information that enters consciousness is at some stage carried by neurophysiological processes that exist at the “classical level” of reality (i.e. in processes where quantum effects have a negligible effect).
But it is possible that the information that is experienced in consciousness is carried by some much more subtle medium analogous to the quantum field but capable of much more complex properties, including qualia, subjectivity and conscious experience.
This information then typically “acts downwards” toward the more manifest levels of the brain, ultimately guiding behaviour.
But how could such a “very subtle” field carrying information possibly be able to act upon the more manifest processes e.g. in the motor cortex? one possibility is that it would act via the quantum field.
“…that which we experience as mind, in its movement through various levels of subtlety, will, in a natural way ultimately move the body by reaching to the level of the quantum potential and of the ‘dance’ of the particles. There is no unbridgeable gap or barrier between any of these levels. Rather, at each stage some kind of information is the bridge. This implies that the quantum potential acting on atomic particles, for example, represents only one stage in the process.”
Bohm was not too specific about what he meant by the “various levels of subtlety”. Are these new types of fields, similar to but more complex than the quantum field? Or can they include levels of processing in the more classical domains of brain function (e.g. the various levels of processing of visual information).
I think Bohm’s view was quite inclusive he did not deny the obvious role which classically describable processes play in the processing of information that enters consciousness (see Bohm & Hiley 1993: 179).
However, I also think he felt that the more subtle aspects of mind and conscious experience involve more subtle levels of information, which have not yet been discovered by cognitive neuroscience. the discovery of the quantum potential is very important as a first guide to what the nature of such more subtle levels could be.
Indeed, Bohm suggested that by extending the ontological interpretation in a natural way, we could include the subtle mental aspects into the theory. but how can such an extension be done?
“… one could begin by supposing … that as the quantum potential constitutes active information that can give form to the movements of the particles, so there is a superquantum potential that can give form to the unfoldment and development of this first order quantum potential. This latter would no longer satisfy the laws of the current quantum theory, which latter would then be an approximation, working only when the action of the superquantum potential can be neglected. Of course, there is no reason to stop here. One could go on to suppose a series of orders of superquantum potentials, with each order constituting information that gives form to the activity of the next lower order (which is less subtle).”
This, then, is a schematic view of the way “mind acts on matter” in Bohm’s extended ontological interpretation of the quantum theory.
Bohm’s solution has two parts. on the one hand he argues on the basis of quantum theory that matter has far more subtle properties than Western mechanistic science has thus far assumed.
on the other hand he suggests that minds are very subtle but adds that it is a mistake to assume that minds are entirely non-physical. instead he assumes that every mental process has a subtle physical aspect which carries the information that is part of the essence of that process.
Quantum theory is important even for the latter hypothesis for quantum theory makes plausible the idea that it is possible for there to exist very subtle physical processes. In Bohm’s extended quantum theory these physical processes are assumed to be so subtle that they can justifiably be characterized as “mental”.
In my view, this is to date the most elegant attempt to tackle the problem Descartes left behind himself: how can mind and matter, which seem so completely different, nevertheless manage to influence each other?
Science seeks that which is general and necessary Bohm’s new proposal: information is general and its action is necessary -> active information as a universal principle Active information helps us to understand the nature of mind/consciousness if active information is (part of) the essence of mind, and if active information is similarly essential in various levels, all the way to the fundamental laws of physics, it helps us to find a place for mind in nature!
Bohm, D. (1990) A New Theory of the Relationship of Mind and Matter. Philosophical Psychology vol. 3 no. 2, pp. 271-286 Bohm, D. and Hiley, B. J. (1993) The Undivided Universe: An Ontological Interpretation of Quantum Theory. London: Routledge Hiley, B.J. and Pylkkänen, P. (2005), “Can mind affect matter via active information?”, Mind and Matter, vol. 3, no. 2, 7-26. Url: www.mindmatter.de/mmpdf/hileywww.pdf Pylkkänen, P. (2007) Mind, Matter and the Implicate Order. New York and Berlin: Springer. Towler, M. (2009) Pilot-wave theory, Bohmian metaphysics, and the foundations of quantum mechanics, a graduate course at the Cavendish Laboratory, University of Cambridgehttp ://www.tcm.phy.cam.ac.uk/~mdt26/pilot_waves.html For criticisms of Bohm’s approach, see the entry “Bohmian mechanics” by S. Goldstein in the Stanford Enclyclopedia of Philosophy. See also Riggs, P. (2009) Quantum Causality: Conceptual Issues in the Causal Theory of Quantum Mechanics. Heidelberg and New York: Springer.